I have BBK longtubes with catted X pipe , GT resonators and Ford Racing Sport axle backs. There is still rasp in the 3500 rpm range but other than that, the sound is awesome.
I don't think you can entirely eliminate the rasp. After all, it is a 6 cylinder, and it is, what it is.
2011 GT. Grabber Blue. Procharged. 3:73 manual.Billit LCA's. Corsa Extremes. GT 500 wheels. Racemaster DR's. T-56 Tremec. Dynotech DS . Centerforce DF. American Racing headers/high flow cats 560 rwhp.Donny Walsh tuned
2012 Pony Package. Race Red.3:31 automatic.BBK longtubes and catted X.FRPP Sport axlebacks. BBK throttle body. Dynotech DS. Brembo wheels and tires. Strut tower brace. Airraid CAI. Bama tuned.